How to use the Body Surface Area
- Enter height in centimetres and weight in kilograms.
- Read BSA from the Mosteller formula.
- Compare the Du Bois result, which usually differs by a few percent.
- Use the figure only as reference — clinical dosing must be prescriber-verified.
How the calculation works
Mosteller gives BSA = √(height × weight ÷ 3600), which is simple enough to do mentally with a square root. Du Bois uses 0.007184 × height^0.725 × weight^0.425 and predates it by decades. The two agree closely in mid-range adults and diverge at the extremes, with Du Bois tending to underestimate in obesity.
Typical adult BSA is 1.6–2.0 m², and many protocols cap dosing at 2.0 m² to avoid overdosing large patients, since BSA-based dosing was never validated at the extremes. Cardiac index is cardiac output ÷ BSA, and the Parkland formula for burn fluid resuscitation uses percentage of BSA burned rather than absolute area. None of this replaces clinical judgment: dosing decisions belong to the prescriber.
Mosteller: BSA = √(cm × kg / 3600) ; Du Bois: 0.007184 × cm^0.725 × kg^0.425Source: Mosteller (1987) NEJM simplified BSA formula and Du Bois & Du Bois (1916).
Worked example
A patient 174 cm tall weighing 82 kg.
- Mosteller: 174 × 82 = 14,268.
- 14,268 / 3600 = 3.963.
- √3.963 = 1.99 m².
- Du Bois gives 1.97 m².
About 1.99 m² by Mosteller — right at the 2.0 m² cap many dosing protocols apply.
Frequently asked questions
Which formula should I use?+
Mosteller is the most widely used clinically because it is simple and agrees well with older formulas.
Why dose by BSA rather than weight?+
BSA tracks metabolic rate and organ function better than weight, particularly for cytotoxic drugs.
Is BSA capped in practice?+
Many protocols cap at around 2.0 m², since the dosing evidence does not extend to very large patients.
Can I use this for clinical dosing?+
No. It is a reference calculation. Dosing must be verified by the prescribing clinician.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.